Canada’s spring runoff outlook increased

April 9, 2013

The Saskatchewan Water Security Agency's April Spring Runoff Outlook released Monday contains some significant changes to the March issuance for the Canadian portion of the Souris River Basin, including an increase in estimated runoff volume of 1.5 to 2 times from a month earlier.

The outlook states, "In the Souris River Basin, the estimated peaks and runoff volumes above Boundary and Rafferty reservoirs have been revised significantly higher."

However, notes the outlook, "sufficient flood storage exists in Rafferty Reservoir to store Souris River inflows and diversions from Boundary Reservoir."

"I had the opportunity Monday to present the April outlook to the Saskatchewan legislature," said Ken Cheveldayoff, Minister of the Saskatchewan Water Security Agency. "We learned some lessons from 2011. Our officials are in constant contact with North Dakota and Manitoba to make sure we are all on the same page."

Despite Cheveldaykoff's assurances, the latest outlook raises some cause for concern about possible high flows for many areas of Saskatchewan, including the Souris basin. A variable that can greatly affect the status of the runoff is the weather, which has been running several degrees below normal very late into what normally would be the runoff season.

"We remain very concerned because of the weather forecast for below normal temperatures for the next 10 days or so," Cheveldayoff said. "Our concern is its going to be very nice and we get into a situation where we may be on the alert for peak flows."

According to the latest Saskatchewan outlook, the Souris River and Moose Mountain Creek drainages are considered to be in the "well above normal" to "very high" runoff regions.

An additional concern is the amount of possible runoff that could enter Long Creek, which has its source in southern Saskatchewan, crosses into North Dakota and then flows back into Boundary Reservoir near Estevan, Sask.

"Inflows are now expected to exceed the capacity of Boundary Reservoir and the Rafferty diversion channel, necessitating a spill downstream," states the outlook.

Admittedly difficult to predict, the outlook estimates the a possible Boundary release into the Souris at 2,119 cubic feet per second to 2,825 cubic feet per second. How long such a flow would be necessary, if at all, won't be known until the runoff gets under way.

Boundary Reservoir is the smallest of the three key impoundments influencing flows on the Souris River. The largest reservoir, Rafferty, is now projected to peak at 1,811 feet. Overflow level is 1,818 feet. Alameda, which backs up Moose Mountain Creek near Oxbow, Sask., is projected to peak at 1,844 feet. Overflow at Alameda is 1,860 feet.

An important number to Souris River interests in North Dakota is the projected peak flow where the Souris enters the state near Sherwood. It is anticipated that flow will peak near 3,170 cubic feet per second. The International Agreement governing flows on the Souris contains a target maximum of 3,200 cfs at the Sherwood crossing.

Last week, Saskatchewan WSA hosted an informational open house at Estevan to provide citizens with information and advice about the upcoming runoff. Other such events will be held at other locations in Saskatchewan in the coming days.

"It gives people a chance to take a look and become more informed," Cheveldayoff said. "It was very well-attended in Estevan."

The latest release rate into the Souris from the trio of Saskatchewan reservoirs is slightly less than 2,500 cfs. Releases from Lake Darling Dam remained at 2,800 cfs Monday afternoon, a rate that has remained steady since last Friday.

According to the U.S. Army Corps of Engineers the goal has been to reduce Lake Darling to 1,593 feet to create more storage for runoff and then reduce the amount of water being released during the melt. Lake Darling was at 1,593.86 feet Monday afternoon, a reduction of about two feet from a few weeks ago.